1. Field of the Invention
The invention relates to a locking system for panels with edge profiles provided on at least two opposite edges of the panels for the positive connection of similar panels, including an edge profile designed as a groove profile, with an upper groove wall and a lower groove wall, and an edge profile designed as a tongue profile, with a notch projection on the underside of the tongue that engages a notch recess in the lower groove wall of an adjacent panel in the assembled state, where the engaged edge profiles form an articulated joint that acts to restore the panels to their installation plane when deflected either up or down. The invention also relates to a panel with the locking system according to the invention.
2. Background of the Prior Art
Locking systems of this kind are used for floor panels, for example, such as parquet panels with a natural wood surface or laminated panels. The latter have a core made of MDF, HDF or particle board and are provided with a reproduced surface made of a decorative laminate.
299 11 462 U1 discloses a generic locking system, whose connection has the function of an articulated joint. Locking systems of this kind are used for floor coverings, which, for example, lie on uneven bases or must bear deflection in the connection area due to the presence a soft backing, such as impact sound insulation. Deflection of the connection causes high stresses in the region of the tongue-and-groove profiles of two locked panels, because the connection bends under the load. The panel material cannot withstand the high stresses in the region of the edge profiles and fails in the connection area.
The ease of installation of the known jointed locking system leaves much to be desired. Its resistance to being pulled apart in the installation plane does not meet expected, future quality standards for floor coverings with mechanical locking systems. Furthermore, the known joint connection can be installed in two ways, where the second installation method described is associated with the undesirable side effect that the connection displays particularly low resistance to being pulled apart.
According to the first installation method, a new panel, preferably tongue-first, is placed at an angle against a laid panel and then folded or rotated downwards until it lies in the common installation plane of the panels and locks automatically.
In the second installation method, locking occurs when both panels are in the installation plane, namely by sliding the panels laterally towards one another. The panels can only be joined together in this way because the undercut between the notch projection of the tongue and the notch recess in the lower groove wall is designed to be correspondingly small. The notch connection achieved in this way is of such low strength that gaps can form between abutting surfaces of adjacent panels due to normal changes in length of the floor. This is the case, for example, when the temperature of the floor fluctuates. This method of jointing also results in immediate damage to the edge profiles, because they must be subjected to strong deformation in order for the undercut of the tongue and the lower groove wall to engage.
Furthermore, the tongue of the known locking system has a long, tapered shape. The top of the tongue has an inclined surface that is intended to facilitate insertion of the tongue tip into the groove. In reality, however, the tongue proves to be very easily damaged due to its tapered shape. This has a disadvantageous effect on the product's ease of installation, service life and utility.
The object of the invention is to design a locking system for an articulated panel connection, which is easier to handle, displays greater resistance to being pulled apart and has a longer service life than the known locking system.
According to the invention, the object is solved in that the upper groove wall has a flank on the inside that opens towards the free end of the groove wall.
Providing a flank on the upper groove wall creates a wide groove opening on the groove side of a panel, into which the tongue profile of an adjacent panel can be inserted more easily than the known, tapered tongue profile into the narrower groove opening of the known locking system.
The flank preferably transitions into a levelling surface extending towards the groove base, which ensures exact vertical positioning without vertical offset between locked panels. In other words, the segment of the inside of the upper groove wall running from the flank to the base of the groove forms the levelling surface, the distance of which to the surface of the panel is precisely equal to the distance of the top side of the tongue to the surface of the panel, meaning that no vertical offset occurs between locked panels.
The flank can be of curved or plane design, where a straight shape is expedient for manufacturing purposes and a curved shape is somewhat more favourable for the panel joining procedure in terms of stress. When the tongue profile comes into contact with the curved flank of the groove profile, the surface pressure is somewhat lower than in the case of contact between the tongue profile and the edge on the end of the plane flank.
A levelling surface is also provided on the top side of the tongue, which interacts with the levelling surface of the upper groove wall when the panels are joined. Since the upper groove wall has a flank on the free, front end, the levelling surface of the tongue is only in partial contact with the levelling surface of the upper groove wall, namely in the region of the free end of the tongue. If the levelling surface of the tongue were in contact with the upper groove wall along the entire length of the top tongue surface, a rigid connection would result. The flank lends the connection a degree of flexibility that favours the joint function of the connection and reduces stress in the material of the edge profiles.
In the event of deflection of the connection towards the installation base, in particular, the flank creates room for movement, so that the top side of the tongue can be moved towards the flank without coming up against it prematurely. The flexibility of the connection achieved in this way enables articulated movement without rupturing the tongue or damaging the groove walls due to excessive stress.
The handling and service life of the locking system are improved if the tongue length, meaning the distance by which the tongue protrudes beyond the upper edge of the panel, is less than or equal to the thickness of the upper groove wall of the groove profile. A tongue of this length is short compared to the prior art. The short tongue has the advantage that only a relatively short insertion path has to be travelled when the tongue is inserted at an angle into a groove profile. Consequently, the proposed locking system is particularly easy to handle during installation and can be installed much more quickly than the known locking system.
The tongue has a blunt surface on its free end, which is more robust and durable compared to the tapered shape of the tongue of the known locking system.
The groove depth of the groove profile, meaning the distance the groove recedes beyond the upper edge of the panel, is favourably greater than the tongue length described above by roughly half. In other words, if the groove depth starting from the upper edge of the panel is 3/3, the tongue protrudes into the groove by a tongue length of ⅔ when two panels are assembled, leaving a space with a residual depth of ⅓ the groove depth between the free end of the tongue and the groove base. Such a large groove depth would not be necessary to simply accommodate the tongue in the groove. However, the large groove depth influences the flexible length of the lower groove wall protruding freely from the edge of the one panel. This makes the connection flexible, reduces stress in the material and thus increases the service life of the connection.
The flexible length of the lower groove wall preferably roughly corresponds to the thickness of the panel. This is because the spring travel required on the free end of the lower groove wall is then relatively short referred to the length of the tongue, and the elastic expansion occurring during joining of the panels causes only little stress in the material, which can be withstood without difficulty.
The depth of the recess in the lower groove wall expediently amounts to roughly one-third the thickness of the tongue. This results in a degree of undercut in the assembled state that prevents the panels from being pulled apart in installed state under normal conditions of use. Compared to conventional mechanical locking systems according to the prior art, which are locked by means of horizontal sliding in the installation plane, the degree of undercut of the locking system according to the invention is roughly doubled and, as a result, the resistance of panels against being pulled apart in the installation plane dramatically increased.
For the purpose of material-saving manufacture, the offcut dimensions on the edges of the panels are relatively small. They preferably differ on the groove side and the tongue side.
On the groove side of a panel, the resulting offcut of the decorated surface is favourably less than half the panel thickness.
On the tongue side of a panel, the resulting offcut of the decorated surface is preferably roughly between ⅓ and ¼ the thickness of the panel. It essentially corresponds to the length the tongue protrudes beyond the upper edge of the panel.
A panel, particularly a floor panel, is expediently equipped with a locking system according to the invention. The locking profile is preferably used for laminated flooring panels, which comprise a core material made of HDF, MDF or particle board, where the edge profiles of the locking system are milled into the edges of the panels.